Wen es interessiert - habe das Problem inzwischen mit JavaScript gelöst:
function getSelectedFiles() {
var inputElements = frames.files.document.getElementsByTagName("input");
var files = new Array();
for (var i = 0; i < inputElements.length; i++) {
var inputElement = inputElements[i];
if (inputElement.checked) {
files.push(inputElement.value);
}
}
return files;
}
function appendHiddenFields() {
var form = document.createElement("form");
form.target = "_self";
form.action = "index.php";
form.method = "post";
var files = getSelectedFiles();
for (i in files) {
var field = document.createElement("input");
field.type = "hidden";
field.name = "file[]";
field.value = files[i];
form.appendChild(field);
}
form.style.display = "none";
document.body.appendChild(form);
form.submit();
}